Malignant lymphoma is a tumor that originates from lymphoid tissues. Its types are classified into Hodgkin's lymphoma and non-Hodgkin's lymphoma. The malignant lymphoma is treated mainly by radiotherapy and chemotherapy using anticancer agents. The malignant lymphoma is difficult to cure or may recur, because this tumor can affect the whole body.
In recent years, a chimeric antibody rituximab directed against CD20has been prepared. This antibody exerts significant antitumor effects on B cell lymphoma, one type of non-Hodgkin's lymphoma, and also has limited adverse effects (Non Patent Document 1). Rituximab alone, however, is low effective for some cancers. Although the combination therapy of rituximab with cyclophosphamide, doxorubicin, vincristine, and prednisolone has been adopted, the development of more effective therapeutic agents has been desired (Non Patent Documents 2 and 3). Accordingly, an antitumor antibody targeting a new antigen has been required. A monoclonal antibody against MHC class II is expected to have anti-malignant lymphoma activity as a clinical antibody recognizing an antigen different from that recognized by rituximab. Unfortunately, an anti-MHC class II antibody, for example, an antibody against HLA-DR, has previously been developed, but has not been used as a therapeutic agent (Patent Document 1).